Manufacturing plants, grocery stores, delivery companies all have COVID-19 outbreaks in GTA|CANADA

© Michael Wilson/CBCShoppers wait outside a Toronto shopping centre in early May. Grocery stores, according to local public health units, are among the workplaces facing COVID-19 outbreaks.

Manufacturing plants, grocery stores, delivery companies and other workplaces are all among the settings where community COVID-19 outbreaks are happening across the Greater Toronto Area, according to public health details shared with CBC News.

Now, as more businesses reopen, officials in the epicentre of Ontario's novel coronavirus cases are keeping a close eye on these indoor workplaces — and multiple infectious disease experts agree it needs to be a key focus.

"Work environments where there's lots of people clustered in close proximity, those are just high-risk places for this to be spread," said Dr. Isaac Bogoch, an infectious disease specialist with the University Health Network.

"It would be very smart to have high-risk settings identified now and if there is excess testing capacity, these are the settings where surveillance systems would be of the highest yield."

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Throughout this months-long pandemic, institutional outbreaks — in settings like long-term care homes, retirement homes and hospitals — have largely driven up case counts and dominated headlines.

But some public health units say those cases are now falling, while community outbreaks were observed even before provincial restrictions started lifting.

Various types of indoor workplaces and factory settings are all hot spots, according to the latest details provided to CBC News by Toronto, Durham, York, and Peel region public health units. Halton was also contacted, but officials did not respond to questions by the deadline for this story.

As previously reported, those five GTA regions make up 76 per cent of the roughly 6,600 new confirmed infections across the province in May.

"We still have a very real threat of community-level spread of the virus," said physician epidemiologist Dr. Nitin Mohan, a partner at ETIO Public Health Consultants and adjunct professor at Western University.

2 'clusters of cases' at Toronto grocery stores

Dr. Vinita Dubey, Toronto's associate medical officer of health, said so far, community outbreak investigations in Toronto have focused on essential workplaces and an emergency child care centre.

"Before the restrictions were put in place, social gatherings were often associated with clusters of cases and outbreaks," she added in a statement.

Toronto Public Hea